I guess I did not explain the problem too well. When the user enters characters in the data field, the requrement is to first disable the length field, and then add 1 to the length field for every character the user types. The length field should be updated immediately, the user hits the key.
I am not familier with the sync method you mention will it work in this case? Could you post a URL for the manual page, or even better, an example. I am new to Utlimate++.